The present invention relates to apparatuses and processes adapted to produce coil members having a fork-like shape, or different shapes, by bending at least one electric conductor.
Once formed, said coil members are inserted into slots of a core of an dynamo electric machine. Fork-shaped coil members are commonly called “hairpins” in the industry. Other shapes may have an undulated configuration, as described in European publication EP1372242.
The magnetic core in which the coil members are inserted may be, for example, a stator for an electric motor or for an electric generator.
The hairpin normally has two straight legs connected together by a bridge-like transversal part. As a whole, the hairpin somewhat looks like an upside-down “U”, with the bridge having a cusp-like shape. Each leg has one free end for inserting the hairpin into the slots of the core. The insertion into the slots is done by passing the free ends of the legs through the longitudinal entrances of the slots and by sliding them past the opposite side of the core, until the legs protrude outwards to a certain extent.
According to the prior art, the hairpin is produced from a conductor having a rectangular or circular cross-section. More in detail, the conductor is cut into straight segments of a predetermined length; each straight segment is bent around a mould to take a temporary “U” configuration.
The temporarily formed legs are then inserted into the slots of two concentric rings, which can rotate relative to each other in opposite directions. With the legs inserted in the rings, a rotation in the opposite direction will subject the hairpin to a definitive deformation, thus giving the hairpin its final configuration, i.e. with the legs spread apart by the pitch required for inserting them into the core slots and with the head deformed accordingly.
In a hairpin production process of common use, after being cut, the straight segment is bent around a first mould to obtain an intermediate hairpin configuration in a plane. The head of the intermediate configuration is then pressed against a second mould to obtain the definitive configuration, wherein the legs are in the correct positions for insertion in the slots. Therefore, this is a process that requires deforming the conductor by pressing it onto suitable moulds.
The apparatuses of common use in the art operate automatically and are not easily adaptable for changes in the geometry of the coil members.
Furthermore, the automatic operations involve pressing the conductor against moulds, and this often places high stresses on the conductor and on the insulation thereof, leading to a high risk of damaging the latter.